Dennis Ugolini waited 17 years to hear a sound that lasted two-tenths of a second. Described as a “chirp,” the sound captured the motion of two black holes, measuring 29 and 36 times the mass of the sun, as they spiraled toward each other into a head-on crash, collapsing into one—a gravitational wave event that occurred more than one billion years ago but did not reach interferometers on this planet until Sept. 14, 2015.
"It sounded underwhelming," he recalls. "That’s ironic because it’s such a cataclysmic thing. The first time many people played that (sound) there were tears in their eyes."
Ugolini, chair of Trinity’s Department of Physics, is one of more than 1,000 scientists who belong to the LIGO Scientific Collaboration to support and conduct research with the Laser Interferometer Gravitational-Wave Observatory (LIGO)—which is actually two facilities in Washington state and Louisiana. The LIGO team measures changes in the curvature of space that happen when objects (such as black holes) move through space. Although space collisions are relatively common, the "chirp" that brought tears to the eyes of thousands of dedicated scientists was the first direct detection of gravitational waves. The event confirmed Albert Einstein’s general theory of relativity introduced more than a century ago in 1915.
Ugolini said the LIGO team had predicted the collision—"We knew it would happen"—but, until it was observed, skeptics in the science community remained. Now that the detection has occurred and the observatories have been accepted as valid instruments, Ugolini said the hope is to continue to record data and observe still more detections, possibly leading to additional physics theories or a deepened understanding of what already has been confirmed. The data may help explain what happens inside the black holes as they collide.
While 17 years seems like an eternity to wait for a scientific confirmation, Ugolini said the project’s three leading scientists waited upwards of 40 years for their research to be borne out. They are Ronald W.P. Drever, professor of physics, emeritus, at Caltech; Kip S. Thorne, the Feynman Professor of Theoretical Physics, emeritus, at Caltech; and Rainer Weiss, professor of physics, emeritus, at MIT. In May, that trio was awarded the Breakthrough Prize in Fundamental Physics for their work, an honor that carried $3 million in award money, and also recognized the contributions of scientists such as Ugolini.
Ugolini earned an undergraduate degree at Caltech and returned there after earning his doctorate at Stanford University to conduct postdoctoral research. Ugolini took a class on LIGO from Thorne as an undergraduate, and when he came back to Caltech to work as a postdoc on a LIGO prototype, he collaborated with both Thorne and Drever. He says he was searching for mentors to help him learn how to take the instrument apart and rebuild it "from scratch," a technique that he has used to instruct undergraduates at Trinity and spark their interest in gravitational waves.
Sean Farrell ’18, who began his junior year at Trinity this fall, recalls sitting in one of Ugolini’s classes last spring and witnessing what the student described as "pure joy" on his professor’s face when the LIGO gravitational wave discoveries were announced. "It must have been life-changing for him," Farrell says.
An engineering science major from Buda, Texas, Farrell plans to minor in mathematics and physics. He expects to attend graduate school to pursue a master’s degree in electrical engineering, and Farrell says conducting research alongside Ugolini has given him a higher understanding on how to use skills learned in the classroom in the "real world."
"Ugolini helped me to become a better student by always (encouraging me) to strive to think deeper and make new connections to solve problems," Farrell says. "This is a skill that I will use not only at Trinity but throughout the rest of my life."
Farrell is one of about 18 Trinity students who have worked in the Ugolini Lab and the second engineering science major. "Half of what I do is engineering," Ugolini says.
Matt Jenkins ’18 from Plano, Texas, was considering graduate school in aerospace engineering until he worked in the Ugolini Lab this summer. Attending graduate school in physics is now "not out of the picture," he said, citing the knowledge he gained from his laboratory research experience with Ugolini. Jenkins said he learned the value of patience since the Farrell-Jenkins team worked two weeks before obtaining any useful data. On a personal note, Jenkins recalls receiving an email from Ugolini one summer night indicating that the professor had found a solution to a research problem while watching the NBA Finals. Ugolini says he wanted students to see that the brain should never shut off.
Jenkins, who is majoring in physics with minors in mathematics and German, said he also observed Ugolini’s excitement in the classroom when the LIGO detection was about to be announced. Once it was, the professor handed out copies to every student of the LIGO journal paper first published in the Physical Review Letters.
Ugolini said every undergraduate physics lab has an interferometer, but as part of their summer research, he directed Farrell and Jenkins to build a small-scale LIGO with mirrors, lasers, converging lenses, and a beam splitter to replicate aspects of the much larger observatory. His lab also contains a vacuum chamber to measure the electrostatic charge on objects, a holdover from a summer he spent at MIT more than a decade ago, when he began working on a project by Weiss, one of the LIGO visionaries.
Farrell presented his research findings at the Gulf Coast Undergraduate Research Symposium in October at Rice University.
Ugolini’s involvement with LIGO has generated interest in his work among Trinity colleagues, prompting organizers of the Distinguished Scientists Lecture to invite the spokesperson for the LIGO Scientific Collaboration, Gabriela González, a professor of physics and astronomy at LSU, to speak on campus in September on "The Discovery of Gravitational Waves from Colliding Black Holes 100 Years after Einstein." When the detection was announced, González said, "This detection is the beginning of a new era: the field of gravitational wave astronomy is now a reality."
According to the LIGO website, LIGO’s gravitational wave detectors were conceived and research and development was initiated in the 1960s. LIGO was built between 1994 and 2002 by Caltech and MIT in partnership with the National Science Foundation of the United States, with the aim of observing the gravitational waves predicted by Einstein’s general theory of relativity. After a major upgrade from 2010–2015, it only took two days to observe a gravitational wave distorting the structure of spacetime as it passed through the Earth. The detected distortion was less than a billionth of a billionth of a meter in size at LIGO’s two 4-km observatories in Hanford, Wash., and Livingston, La. The wave emanated from two black holes with masses about 30 times that of the sun, spiraling into each other 1.3 billion light years away.
After the journal paper was published and the confirmation was announced, LIGO scientists held a news conference attended by major media outlets gathered at the National Press Club in Washington, D.C., and beamed to the 133 LIGO-member institutions (including Trinity) via a live satellite feed. That first much-heralded detection "event" was followed by a second one on Dec. 26, 2015, involving smaller black holes that took longer to combine. Although the first "chirp" lasted two-tenths of a second, the follow-up event lasted for a full second, Ugolini says, providing more data.
After waiting anywhere from 17 to 40 years, scientists were astounded to observe a second "event." In January, the observatories were taken offline for maintenance and upgrades but they were put back into motion this fall.
The next phase of the project will include the two U.S.-based interferometers along with a third one in Pisa, Italy, known as the Virgo interferometer. Ugolini said the third instrument will allow researchers to "triangulate where the gravitational waves come from."
Whether working with fellow physics researchers or undergraduates at Trinity, Ugolini dates a major turning point in his work to GW150914—the year, month, and day of the first confirmation of gravitational waves—and pondering the universal mysteries of what happened that day when two black holes collapsed into one. In recalling the "chirp," he says, "When this collision happened, I couldn’t stop playing that blip, trying to picture the thing that created it."